Process for controlling destructive distillation of petroleum oil



'Fel:.- 7, 1928.

` R. w. HANNA PROCESS FOR CONTRLLING DESTRUC'TIVE DISTILLATION 0F PETROLEUM OIL I Filed Feb. 1 2, 1923 mehrmals. w n

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lwntunteu lPatented Feb. 7, 1928.

y UNITED STATES PATENT OFFICE.

RICHARD W. IIANNA, OF PIEDMONT, CALIFORNIA, ASSIGNOR,A BY .MESNE ASSIGN- MENTS, TO UNIVERSAL OIL PRODUCTS COMPANY, CF CHICAGO, ILLINOIS, .A. COR- PORATION OF SOUTH DAKOTA.

PROCESS FOR CONTROLLING DESTRUCTIVE DISTILLATION -OF PETROLEUM OIL.

Application filed February 12, 1923. SerialNo. 618,607.

This invention relates to the art of destructively distilling petroleum oil, and refers particularly to a process and apparatus by which the cracking reeact-ion is stabilized and controlled so that a uniform product is produced.

Inl the destructive distillation of petroleum oil, the oil is continually cracked and produces lighter or lower boiling oils which are volatile at the temperature and pressure employed in the cracking re-action and vaporize and pass from t-he cracking zone carrying with them a considerable quantity' of the heavier or higher boiling oils. Suc higher boiling o ils are not desired in the product and properly should be returned to the cracking zone forfurther treatment or cracking, or to be withdrawn in the residual oil. For this reason cracking apparatus is frequent-ly equipped with a reflux tower whereby a separation of the desired low boiling point vapors may be accomplished and the heavier oils 'returned to the cracking zone. It is essential to control this separai tion of the product of the cracking re-action so that a uniform product is withdrawn, or the nature of the oil in thecracking vzone will be altered with corresponding variations in the cracking re-action. If the separation of the low boiling point oils from the higher boiling oils is not complete, a considerable quantity of the higher boiling point oils will be withdrawn from the Zone resulting in a decrease in the amountv of such oils that will be .cracked and further requiring a later separation or distillation of the oils to pro duce the desired products. l

Hitherto the destructive distillation' of petroleumToil has been controlled principally by balancing such factors as; the rate of feeding the oil, the rate of supplying heat to the cracking zone, transfer of heat tothe feedoil or radiation of heat to the air so that equilibrium is established and the discharge vapors are substantially uniform in quality. .l

It can be seen then that in a givenl apparatus the factors `which effect the rate of cracking are to aconsiderable degree required to be maintained at those conditions at which thedesired product will be produce and it does not follow that these con ditions governing the cracking re-action are necessarily optimum conditions at. which said cracking re-actioiishould be conducted if the control of the separation of the evolvedy vapors therefrom, was not dependent on these factors.

An object of this invention is to provideA a process wherein the control of the temperature-and nature ofthe discharged product is independent of the regulation of those factors governing the cracking zone whereby the process may be 'more readily maintained under the most desirable conditions for eHecting the cracking of the oil.l v

Anotherobject of this invention is to pro vide a more complete separation of the-desired fractions of low boiling point range from the evolved vapors of the process whereby both an increase of the yield of such desired products, and a decreased expense of later treatment may be attained.

This invention, in one of its broad aspects,-

comprehends that by regulation of the heat dissipation from the evolved vapors of the cracking reaction, so as to maintain a substantially constant temperature ofthe vapors This invention, in one ofits broad-aspects,

comprehends that for the maximum etticiency and control of a destructive distilling operation, a verythorough sifting of the vapors evolved within thesystem, must be effected,-so that not only no vapors except those within a desired boiling point range, are permitted to pass from the'system, but also a minimum amount of the fractions within this range are retained at the crack.

ing zone. This result can be secured by the regulation of the heat dissipated from the evolved vapors, so that the temperature of the vapors discharged can be maintained as desired.

More specificallygthis invention comprehends that by insulating the system from the varying effects of atmospheric conditions and controllably dissipating heat to a medium independent of the cracking zone, the temperature and nature of the discharged vapors may be controlled thereby and regulation of the entire reflux system accomplished, resulting in a more efficient separation of the evolved vapors and stabilizing and bringing such system within ready and possible control of the operator. Moreover, since the regulation of the natureof the discharge product is thereby rendered independent of the cracking Zone, 'the cracking zone may be operated at the optimum conditions desirable in cracking the oil and more effective 'and higher rates of cracking can be maintained in the same apparatus.

This invention may be readily understood in connection with a description of the preferred process embodying the invention as practiced in given apparatus. Reference is therefore made to the accompanying drawings, which illustrate apparatus by which a process embodying the invention may be performed.

In the drawings:

Fig. 1 is a side elevation partially in section.

Fig. 2 is a longitudinal sectional View of the lregulable heat dissipation member.

In the drawings, 2 indicates a still or evaporator in wh-ich the body of the oil undergoing cracking is maintained. Such evaporator is provided with a cyclic heating system comprising conduit 5 communicating with the evaporator 2 at one end and leading through a pump 6, and a continuation of said conduit 7 to a heating coil 3 and hence through a conduit 8 b ack to and re-entering the stillrat the opposite end to which the conduit 5 is connected. 9 indicates suitable valves in the conduits' 5, 7 and 8, which may be employed to regulate the flow of the oil through the heating system. Heatinfr coil 3 is positioned in the furnace 4, which may be directly or indirectly fired, as desired. 10 indicates a vapor line leading from the evaporator and 'entering near the bottom of'a tower 11. In the drawings, at dotted lines, the tower is. indicated as provided with baffle plates arranged in staggered relation so as to cause the ascending vapors to flow in a contorted path. 12 indicates a suitable line from the source of supply of the oil to b e cracked such, for instance, asthe storage tank (not shown). Such line may'` if desired, be led through suitable heat vexchangers or through preliminary heating furnaces before the feed oil is discharged into the center of the tower. Preferably, the incoming oil is delivered by the said pipe 12 onto one of the baffle plates. 13 4indicates a vapor line from the top of the tower, entering the regulable heat dissipation member 14 preferably a short distance above the bottom thereof and atthe Referring to Fig. 2, this member 14 is shown as preferably cylindrical in form and provided with closed ends and with tube .sheets or partitions 35, whichl provide two chambers 36 and 37, at the bottom and top respectively, of the member 14. 38 indicates tubes extending through the tube sheets 35 and through the chamber of the member 14, so that communication from the chamber 36 to 37 is through these tubes 38. In the vapor chamber of the member 14 (between the tube sheets 35) deflection plates 39 are provided so that the vapors entering the chamber from the vapor line 13 are compelled vto circulate back and forth through the chamber in passing upward therethrough; thus contacting repeatedly with the tubes 38 finally passing out through the vapor line 15. Said vapor line 15 leads through a condenser 16 and pressure controlled valves 18 through conduit 17, to storage. It is obvious that the line 15 might pass through vapor heat exchangers and be employed to heat the feed oil, if desired. 40 indicates a conduit for drawingoff the condensate from vthe member 14, and discharging such condensate into the tower l1 at the top thereof, where itis `showered onto the uprising vapors. As indicated by the dotted lines at 41, the line y40 enters into a pan which forms a seal or trap for tower 11 to one end ofthe evaporator 2,

whereby the reflux vand incoming feed ass into the evaporator. 43 indicates a resi ual oil or tar draw-off line.

26 indicates a water line leading from any suitable source of supply and connected "through a pump 25, valve 25 and continuation ,of the line 26 to the chamber 36 of the member 14. The upper chamber 37 of the member 14, is provided with a steam line 43 for discharging steam evolvedin the member 14, which steam may bc discharged directly to the atmosphere through the conduit 4401- may be sent through the line 45 and utilized for various purposes. 28 indicates a niemebr which is connected tothe chambers 37 and 36, by lines 27 and 32 respectively, and which is slightly higher in elevation than the member 14, whereby said member 14 may be filled with water in the chambers 37 and36 and the inter-communicating tubes and the steam envolved withdrawn from the member 28 through suitable lines 29 and 30. 31 indicates suitable valves whereby the pressure in the members 14 and 28 may be maintained at any desired point permitting a regulation of the degree of heat dissipation in the member 14. 33 \indicates a suitable level indicating device connected to the member'28. 20 and 21 indicate suitable temperature indicators connected to temperature actuated devices indicated at 22 and 23 respectively, which indicate the temperature of the discharged water or steam from the member 14 and the temperature of the discharged petroleum vapors therefrom.'

In order to counteract any changes in temperature conditions, due to changes of weather, and properly retain the' heat dissipation within the regulable control of the operator, all of the apparatus from the evaporator 2 to the entrance of the condenser 16, is suitably insulated to prevent the dissipation of the heat, This insulation is not specifically indicated in the drawings.,

It, however, may consist of asbestos sheets and plaster properly applied or any other heat insulation. The heat dissipation member 14 may be operated in two different manners. Thus water may be fed to the member 14 at such' a rate as to compensate for evaporation losses and to maintain vsuch a level 1n the member`14, that the correct amount of effective cooling surface will be in contact with Jche vapors so as toy bring .about the desired temperature of the discharged vapors, the fractions condensed from the vapors because of the resultant reduction of the temperature, are those not desired'in the final promaintained on the cooling medium within` such member by opening directly to the atmosphere or by means of valves or other suitable devices. In this manner of using the member 14, the steam evolved is drawn off through the-line 43.

In some instances, it will be found preferable to maintain the chambers 36 and 37 and inter-communicating tubes filled with the coolingmedium, in which case the regulation of the rate of heat dissipation is accomplished by varyin the temperature-of the cooling medium. his is done by the control of the pressure and thereby the boilii'ig point of the cooling medium through the controlledrclease of the vapors from the upper part of member 28, by means of valves 29 and 31.

It is recognizedthat by modification of the member 14 it might be possible to effect corlrect dissipation of heat by flowing' a liquid noted that in this part of the tower, the upcoming vapors are in Contact onlywith the condensate of said vapors and thereby a thorough sifting ofthe lighter" fractions from the heavier is obtained. At a point lower in the tower the feed line enters and, below this point, the upcoming vapors are exposed to and commingled with the descending feed oil together with the refluxr present from the partial condensation taking place above. ln this portion of the tower a rough scrubbing `of the upcoming vapors occurs) In this portion of the tower the vapor reflux and said feed oil are brought to substantially the same temperature.

It will thus be seen that by bringing the feed stock into the vapor tower at a point intermediate its ends and bringing the reflux from the heat dissipation member into the vapor `tower at its top, there is provided -a three stage vapor separation or condensation.

(a) The ,rough scrubbing in the tower below the point of feed, (b) the scrubbing by the condensate from the heat dissipation member, and (c) the controlled cooling 'effect of the Kheat dissipation member. By this means, a much more thoroughsifting of the heavier or higher boiling fractions from the evolved vapors is attained than has hitherto been possible without re-distillation. It has also been found that by the use of the controllable heat dissipation of the evolved vapors, combining with the two lower stages to produce the three stage reflux rocess, the destructive distillation of petro eum oil may be carried on at the proper conditions desirable for the most efficient crackingof the oil, the controllable feature of heat dissipation member making the change in rate of firing, rate of feed or change in other Variables unnecessary `for the production of desired distillate, thus permitting the stabilizing vof the entire process under the most desirable condition for cracking. The operator is enabled to control the temperature of the discharged vapors, so that a distillate of uniform boiling point range is produced even where the rate of cracking varies.

It is understood that the process and apparatus therein described is only one illustration of the invention which is not limited nis to the specific process and apparatus, but is of the scope set forth in the accompanying claims.

I claim:

1. A process of destructively distilling ,petroleum oil which comprises distilling an oil under the requisite temperature and pressure to decompose such oil While permittin the products to vaporize, passing the evolve vapors through a three stage separating system under the pressure of the cracking reaction in the first stage of which system the evolved vapors pass upward against a descending shower composed of the feed oil to the cracking process and the reflux descending from the second stage, in the second stage are scrubbed against the descending shower of condensed vapors from the third Stage, and in the third stage are brought to a desired discharge temperature by dissipation of heat t0 an independently controlled liquid cooling medium other than the liquid undergoing distillation, and continually passing the combined reliux from the vapor separating system together with said feed oil to the cracking chamber.

2. A process of destructively distilling petroleum oils which includes subjecting petroleum oil to the requisite conditions of temperature and pressure to decompose such oil while passing the evolved vapors through a three stage vapor separating system under the pressure of the cracking reaction, in the first stage of which the evolved vapors are caused to ascend against a descending shower of feed oil to the cracking chamber, together with the reflux descending from the second stage, in the second stage the vapors are subjected only to scrubbing action of a shower of the condensed vapors from the third stage, and in the third stage are brought to a desired discharge temperature by regulation of the supply of an independent cooling medium, said cooling medium being a liquid other than the liquid undcrgoing distillation and being maintained at its boiling point.

3. A process of destructively distilling petroleum oil which comprises distilling an oil under the requisite conditions of temperature and pressure to decompose such oil while permitting the products of decomposition reaction to vaporize, passing the evolved vapors through a three-stage vapor separating system under the pressure of the cracking reaction in the first stage of which system the evolved vapors pass upward against a descending shower composed of the feed oil of the cracking process and the reflux descending from the second stage, in the second stage the vapors are scrubbed against a shower of condensed vapors from the third stage, and iii-the third stage are brought to a desired discharge temperature by dissipation of heat from the vapors to a liquid cooling medium said liquid cooling medium being other than the liquid undergoing distillation. said liquid cooling medium being maintained at its boiling point and under pressure, and continually passing the combined reiux from the vapor separating system together with said feed oil to the cracking-chamber.

Signed at Richmond, California, this 31st day of January, 1923.

RICHARD W. HANNA. 

